Conventional hand-held thermometers may facilitate measuring the temperature but are not very accurate in measuring the temperature of the surfaces or of the air flows. Also, the conventional hand-held thermometers are not effective in measuring temperature the temperature of remote places as the distance between the thermometer and the place of interest can cause errors in the reading. This a significant problem for HVAC (Heating, Ventilation and Air Conditioning) devices.
There are two types of thermometers that are most commonly used in the HVAC field for measuring the temperature in an operating forced air unit. A first type is the electronic probe thermometer, more commonly recognized as a meat thermometer. This type of thermometer has a rigid pointy probe (metal probe) that one, in cooking applications, would stick into the center of a cooked roast. The electronic probe thermometer works by generating a small current across the electrodes of the metal probe, measuring how much current flows through the probe and thus the electrical resistance across the probe. Inside the thermometer, a microchip is used to convert this resistance into a temperature measurement that is displayed on the screen of the thermometer. The screen is provided on the opposite side of the probe, in front of the user, for enabling the user to see and record the temperature. This type of thermometer is also used in the HVAC field, and it comes in different shapes of housing. The electronic probe thermometer is without a doubt the most accurate thermometer and the most trusted for accuracy by a HVAC technician for many years.
However, all versions of electronic thermometers in the HVAC field use the same rigid straw-like metal probe with a pointy end to obtain air temperatures.
A disadvantage of using an electronic probe thermometer for obtaining air temperatures for HVACs is when a HVAC technician is seeking air temperature in a conditioned space. In this case, in most settings (90%), the technician needs a ladder because the metal air vent register that conditioned air is blowing out of, is in many cases over 10 feet above the floor. Therefore, in this scenario a technician would walk into a home, set up a ladder, climb the ladder to get within arm's length of the of an air supply grill to measure the temperature. He/she would then pull out a probe thermometer and insert the rigid probe inside, or very near, the air vent register so that the stream of conditioned air passes over the probe triggering the display unit to show the temperature on the screen. However, the correct temperature of the air is not provided immediately; it can take a few minutes for the probe thermometer to read the true temperature of the air. The main factor for the time delay is that the thermometer has been stored in a tool bag that has been sitting in a hot environment outdoors therefore heating up the probe of the thermometer. So, when being used to measure cold air, the cold air stream must first cool down the hot probe then bring it down to conditioned air temp. The hotter the probe, the longer the wait for accurate air temperature blowing from the air vent. Because of this, an HVAC technician might have his arms up holding the probe in a fixed position on a ladder for up to 4 minutes. This can be very tiering and frustrating for the technician.
To reduce the strain of the art held-out for such a long time, some technicians use a piece of duct tape and tape the thermometer to the air vent with the probe inside the grill to catch the air temperature, freeing the arms from holding the thermometer. This allows the technician to save time and perform other tasks as for example to check the refrigerant level or change the filter while the thermometer is taking time to record accurate air temperature. After the technician has recorded the air temperature coming from the air vent and the thermometer is no longer needed, the technician must climb back up the ladder, remove the tape and detach the probe thermometer from the air vent.
To summarize, the probe thermometer is the most accurate device in use today, but it requires the use of a ladder or the like for obtaining air temperature from air vents which is inconvenient and time consuming.
A second type of thermometer is a hand-held infrared laser thermometer which does not require the use of a ladder when seeking air temp from elevated air vents in the ceiling. With the infrared laser thermometer, a technician can be at ground level and shoot an infrared laser beam at the surface of the air vent and get near accurate air temperature. This measurement is displayed on a digital screen that is located on the hand-held device. This thermometer is convenient because no ladder is needed and it can provide temperatures on air vents that are hard to access even with a ladder because of obstructions like furniture or shelves.
However, it is well recognized that these infrared devices display wrong temperature readings; the readings may be so far off the technician knows there is a malfunction. The cause of errors in infrared thermometers include the reflection of radiation from a hotter body rather than radiated by the object measured. Sometimes, especially near ambient temperatures, the readings may be subject to error due to the body of the person holding the instrument. Also, the infrared thermometers do not capture the temperature of the air itself but only of the surface of the grill near the flowing air. For example, a user can take a temperature reading from 8 feet and get a reading of 105° F. At this distance, the user can feel the air from the air vent blowing and assume the reading will be between 75° F. and 80° F., to immediately realize that the reading is wrong.
Moreover, infrared laser thermometers are expensive since they employ infrared technology. In addition, conventionally, the measured temperature readings are temporarily stored in the memory of the thermometer and are then recorded manually by the user. Manually recording the temperature is prone to human errors. Also, the recorded temperature readings are prone to loss since the readings are stored temporarily. Conventionally, there are no ways of extracting the temperature reading from the telescopic thermometer.
To summarize, the infrared thermometer is convenient because no ladder or the like is required to obtain near accurate air temperature readings from an air vent, but it is an unreliable source if an exact air temp is desired by a technician.
Considering the pros and cons of both the probe type and the infrared laser type thermometers, there is need to have a thermometer that would give an accurate air temperature reading like a probe thermometer and at the same time be able to reach air vents and read air temperature of air vents or inside the air vents that are out of reach, without the use of a ladder like a infrared thermometer.
It is extremely important to use accurate air temperature readings in the formula for calibrating the operation of an AC system, called target super heat and sub cooling formula, to obtain a system running at maximum efficiency. Another important formula that requires accurate air temperature measurements is called the “temperature split” which is uses the difference in temperature between the return and supply air temperatures. Temperature split formula is used in almost every service call in the HVAC industry.
Also, there is a need to enable proper record keeping for the temperature readings, in order to enable comprehensive maintenance and repair for HVAC devices.
It is to be noted that while the specification describes the preferred embodiments with reference to the HVAC field, the telescopic thermometer presented here may be used in any other field of activity where remote measurements are necessary.